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Thread: Spark Plug Gapping...postives and negatives for...

  1. #1
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    Spark Plug Gapping...postives and negatives for...

    Gapping higher

    Advantages
    Disadvantages

    Gapping Smaller

    Advantages
    Disadvantages




    Discuss.
    M3 Sedan Club President #21

  2. #2
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    larger gap = more power, better combustion.
    larger gap = easier to blow out with FI

    smaller gap = less power, reliable spark
    smaller gap = harder to blow out at high psi

    key is to gap plugs as wide as possible before you get spark blow out.
    1005whp/831wtq little bit of low boost pump gas magic...

  3. #3
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    Im assuming bigger gap = better gas mileage as well yes?
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  4. #4
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    So where is everyone gapping @ I'm @ .025 with A 7 heat range from NGK

  5. #5
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    I am also at .025 with the 7 bpr7es ngk

    spark blows out at just 8psi around 4500rpm if you forget to gap them down to .025 haha

    I didnt notice a change in milage when I swapped plugs and gaps... I have a msd blaster coil that I think ignites my mix pretty well either way.

  6. #6
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    My car was missing at .025" at 18psi with Bkr7e's

    I switched to R5671A-8's gapped to .022" and they have been working great so far (about 75 miles)

    According the NGK's website if your plug tip is white then your plug is running to hot.
    -Kyle 1995 Custom Turbo M3 SOLD!

  7. #7
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    Quote Originally Posted by jfdmas View Post
    larger gap = more power, better combustion.
    larger gap = easier to blow out with FI

    smaller gap = less power, reliable spark
    smaller gap = harder to blow out at high psi

    key is to gap plugs as wide as possible before you get spark blow out.
    perfect post
    /thread
    ESS 625
    RAGE AGAINST THE MACHINE

  8. #8
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    Funny this thread is today. I am good to 17psi at .027 gap on a 9 heat range plug.

    When I try to boost past 17psi I blow out spark.

    I have gapped down to .022-.018 and have had the same results.

    In my bag I have a friends plasma coils and a set of 8 heat range plugs.

    I am going to start at .035 and gap down to .020 to hit 25psi.

    Btw, I am running 110 octane at 19 degrees total timing.
    TEC-3R, T4 GT40, WISECO, EAGLE, SUPERTECH, O-RING'D "FRANKENSTEIN" STROKER.

  9. #9
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    Quote Originally Posted by BMuu View Post
    My car was missing at .025" at 18psi with Bkr7e's

    I switched to R5671A-8's gapped to .022" and they have been working great so far (about 75 miles)

    According the NGK's website if your plug tip is white then your plug is running to hot.
    So those were the plugs I was running man

    They are good and cheap, just need alot of maintenance.
    M3 Sedan Club President #21

  10. #10
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    Quote Originally Posted by trthrrt489 View Post
    Funny this thread is today. I am good to 17psi at .027 gap on a 9 heat range plug.

    When I try to boost past 17psi I blow out spark.

    I have gapped down to .022-.018 and have had the same results.

    In my bag I have a friends plasma coils and a set of 8 heat range plugs.

    I am going to start at .035 and gap down to .020 to hit 25psi.

    Btw, I am running 110 octane at 19 degrees total timing.
    If you are still blowing out spark below at .020 gap the coil is bad.
    I ran 30 psi on a 20 gap with the tec 3
    996WHP 2.8 and going nowhere fast
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  11. #11
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    Great topic. I think mine are at .028 which i think is stock(??) and have had some misfire problems at high boost settings...18psi maybe. I thought it was the coils, becasue it was always on the same cyl. could it be that just those 2 cyl have a larger gap then the others?


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  12. #12
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    great topic. i always was woundering this.

  13. #13
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    personally i hate gapping down. I feel its nothing more than a bandaid fix to a bigger problem.

    If you cant fire off the mix with a 0.8 - 1.0mm gap, you really need to upgrade your ignition system. Gapping down does nothing more than produce a colder spark, and increase the risk of fouling plugs.

    Nice hot spark makes a nice strong flame front, which makes for nice smooth even combustion. A weak spark, well ... we all know the "blown out" feeling.


    Bit of a rant, i know, but i really hate gapping down - bloody tight asses, FIX THE PROBLEM, NOT THE SYMPTOM!!
    Fast, Cheap, Reliable - Pick any two, and the third is laughable

  14. #14
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    Quote Originally Posted by tlmitf View Post
    personally i hate gapping down. I feel its nothing more than a bandaid fix to a bigger problem.

    If you cant fire off the mix with a 0.8 - 1.0mm gap, you really need to upgrade your ignition system. Gapping down does nothing more than produce a colder spark, and increase the risk of fouling plugs.

    Nice hot spark makes a nice strong flame front, which makes for nice smooth even combustion. A weak spark, well ... we all know the "blown out" feeling.


    Bit of a rant, i know, but i really hate gapping down - bloody tight asses, FIX THE PROBLEM, NOT THE SYMPTOM!!
    Have any suggestions for ignition systems then?


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    crop2 by justinmdougherty, on Flickr

  15. #15
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    Sorry, no suggestions - im not at the point of needing to fire off a mix in high boost.

    Ill have to do some homework soon tho - my mates almost at the limit of his ignition system in the FC (Second gen) RX7. Afaik, he just needs better igniters to get a bit more life out of the coils.
    Fast, Cheap, Reliable - Pick any two, and the third is laughable

  16. #16
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    I would like to know suggested ignition upgrades as well. Whats recommended with a Tec3r?
    -Kyle 1995 Custom Turbo M3 SOLD!

  17. #17
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    so what would be the best gap for a stock motor on 8-10 psi??

  18. #18
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    With tec 22-26 will work.The tec manual gives refrence on reccomended gaps.
    996WHP 2.8 and going nowhere fast
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  19. #19
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    where could i get a tec management?

  20. #20
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    Quote Originally Posted by card counter View Post
    If you are still blowing out spark below at .020 gap the coil is bad.
    I ran 30 psi on a 20 gap with the tec 3
    You were right! On the dyno, I was frustrated that it was blowing out spark over about 400whp. The guy said "your exhaust vales are floating at high rpm's, you have to much backpresure"

    I made my exhaust and used a $30 Summit muffler(chambered) for the midpipe. I did a pull with an open downpipe and picked up over 100whp.

    The POS Summit garbage killed the power.

    FWIW, I had experimented with .034-.018. The gap of .034 made great power untill about 19psi(thinking Supra land here).

    The moral here is, if you think it's just ignition, it would be wise to test the air flowing in and out of the motor. Not just assume, but, test.
    TEC-3R, T4 GT40, WISECO, EAGLE, SUPERTECH, O-RING'D "FRANKENSTEIN" STROKER.

  21. #21
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    Quote Originally Posted by card counter View Post
    With tec 22-26 will work.The tec manual gives refrence on reccomended gaps.
    Over 19psi I had to gap tp .022 and it worked great. You give good advice...........
    TEC-3R, T4 GT40, WISECO, EAGLE, SUPERTECH, O-RING'D "FRANKENSTEIN" STROKER.

  22. #22
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    Quote Originally Posted by trthrrt489 View Post
    Over 19psi I had to gap tp .022 and it worked great. You give good advice...........
    Glad to hear
    996WHP 2.8 and going nowhere fast
    . e36 4Dr with A/C and leather seats in U.S.
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  23. #23
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    Quote Originally Posted by trthrrt489 View Post

    I made my exhaust and used a $30 Summit muffler(chambered) for the midpipe. I did a pull with an open downpipe and picked up over 100whp.


    You will not find this statement anywhere else on bimmerforums,
    M3 Sedan Club President #21

  24. #24
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    Quote Originally Posted by RRdawho? View Post


    You will not find this statement anywhere else on bimmerforums,
    Get-r-done!
    TEC-3R, T4 GT40, WISECO, EAGLE, SUPERTECH, O-RING'D "FRANKENSTEIN" STROKER.

  25. #25
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    Quote Originally Posted by trthrrt489 View Post
    Get-r-done!
    Waiting for shops to open here so I can get parts...
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